HSA Question spouse has option to get an EPO

I will be enrolling in a HDHP with a HSA in 2018 with my employer.  I will have my wife and college daughter covered on the plan (she is full time student and under 26).

My wife also has the option to get an EPO with her employer to cover herself only.  I only keep her on my insurance because I'm retired and can never add her back if I remove her.

Questions.  Can I pay for any qualified medical expense she has out of pocket if she uses her own EPO?

How much can we contribute to the HSA for all 3 of us, or just me and my daughter?  I'm over 55 as well.